Current, fourth generation wireless communication systems operate at frequencies up to 2.6 GHz. Future generation wireless communication systems are expected to operate at higher frequencies (for example, 30 GHz to 300 GHz), dominantly at millimeter waves (mmW). Advantages of mmW include higher speed, finer resolution, better integration, more compact antenna, and others. However, significant losses due to on-board interconnections, high free space path loss and the effect of radiation from antenna feed networks and circuits are some challenges that need to be addressed for efficient mmW wireless systems.
Conventionally, the architecture of wireless systems involves interconnection of antenna and associated circuits (for example, amplifier) using transmission lines, which are characterized by impedance and other parameters. However, the length of such transmission line interconnections are significant for mmW systems, as it results in severe loss.
Active integrated antenna is another well-known configuration which involves integration of antenna and active circuits on the same board near each other, reducing the interconnections and therefore loss. In rare cases, the antenna functions as a direct load. However, this configuration still has the passive circuitry and interconnections in the vicinity of radiator, affecting the overall radiation performance.